New Insights into the Diversity and Pathogenicity of Fusarium Species Causing Carnation Wilt in Lam Dong, Vietnam

Carnation Fusarium wilt (CFW) is a devastating systemic disease affecting carnation production worldwide, yet little is known about its status in Vietnam. This study provides the first comprehensive report on the population and pathogenesis profile of Fusarium species associated with CFW in Vietnam. A survey of commercial greenhouses revealed approximately 10.7% disease incidence, with symptomatic plants showing chlorosis, wilting, leaf blight, and vascular discoloration. Twenty-one Fusarium isolates were recovered and classified into the Fusarium oxysporum species complex (FOSC) and F. incarnatum-equiseti species complex (FIESC), each comprising two morphologically distinct clades. Molecular identification based on ITS and TEF-1α sequences confirmed four species: F. oxysporum (9 isolates), F. pernambucanum (7), F. sulawesiense (4), and F. nirenbergiae (1), revealing notable species diversity. Pathogenicity tests at the seed germination and transplant stages demonstrated that all species were capable of causing disease, with varying degrees of aggressiveness. FOSC isolates generally delayed germination, while FIESC isolates caused a more significant reduction in germination rate. Both complexes induced root rot, seedling death, and foliar symptoms in transplants. Two highly virulent isolates, C1611 ( F. oxysporum ) and C2111 ( F. pernambucanum ), significantly reduced seed viability and survival and caused high disease intensity. Some isolates showed organ- or stage-specific pathogenicity. This is the first report of F. pernambucanum , F. sulawesiense , and F. nirenbergiae associated with carnation, globally, and the first record of CFW-associated species in Vietnam. These findings highlight the diversity and pathogenic complexity of Fusarium species involved in CFW and underscore the need for accurate identification and effective disease management strategies in local and international trade.